Assays for BNP

Fig. 3. Synthesis and secretion of BNP and proBNP. aa, amino acid; MM, molecular mass.

Table 1

Antibody Characteristics of BNP Assays Cleared by the Food and Drug Administration

Table 1

Antibody Characteristics of BNP Assays Cleared by the Food and Drug Administration

Manufacturer

Capture antibody

Detection antibody

Bayer/Shionogi Biosite/Beckman Abbott

Murine MAb vs ring structure Murine MAb vs ring structurea Murine MAb vs ring structurea

Murine MAb vs C-terminus Murine omniclonal Aba Murine MAb vs C-terminus

"Currently no exact information on epitope mapping on the BNP molecule is available from the manufacturers.

"Currently no exact information on epitope mapping on the BNP molecule is available from the manufacturers.

throughput platform (Access, Beckman Coulter). The assays manufactured by Bayer and Abbott are both for automated laboratory platforms. These immunometric assays for BNP are based on two monoclonal antibodies (MAbs) or a combination of monoclonal and omniclonal antibodies. One antibody binds to the ring structure that is formed by a disulfide bond, and the other antibody binds to the carboxyl- or amino-terminal end, respectively (Fig. 2). Table 1 summarizes the antibody characteristics of the commercially available BNP assays.

Calibration and Standardization

Each assay detects BNP without significant crossreactivity to related peptides (ANP, C-type natriuretic peptide [CNP], urodilatin, NT-proANP and NT-proBNP and fragments) or other peptide hormones. Because the synthesis of proBNP is very difficult, there are no published data regarding the affinity of these assays for the prohormone. Synthetic BNP is used as a calibrator for each of the commercial BNP assays. However, the source of the synthetic BNP varies among assay manufacturers, which makes standardization among assays more difficult. It is important for the clinician to recognize that, similarly to the circumstances for troponin I, the available assays for BNP are not standardized across manufacturers, and, thus, the concentration of BNP reported for the same sample may differ among assays (Table 2) (8-11). Nevertheless, there is acceptable concordance

Table 2

Linear Correlation Coefficients and Regressions Among BNP Assays

Table 2

Linear Correlation Coefficients and Regressions Among BNP Assays

Manufacturer 1

Manufacturer 2

Correlation coefficient

Equation

Biosite

Shionogi

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